Vinyl chloride is industrially produced by reactions represented by the following chemical equations (see, INDUSTRIAL CHEMICALS, 2'd. Ed. Faith, W. L.; Keyes, D. B. & Clark, R. L.; John Wiley & Sons Inc., Publ. New York 1957; pages 798-800):
1. The reaction of acetylene and hydrogen chloride ##STR1##
2 The dehydrochlorination of dichloroethane ##STR2## Hydrogen chloride and acetylene are low molecular weight compounds usually copresent in the uncondensed overhead output stream of processes employing both reactions (1) or (2). Minor concentrations of acetylene are formed in the dichloroethane dehydrochlorination process and accumulate in the fractionated hydrogen chloride by-product stream (typically, at acetylene concentrations between 200 to 4,000 p.p.m. by weight).
Removal of organic impurities from the vapor phase by use of solid adsorbants is favored by low or moderate temperatures (within 50.degree. C. of ambient) which encourage condensation of the adsorbate. Periodically, the adsorvant bed must be disconnected from the vapor phase input for replacement of spent adsorbant or desorption of accumulated adsorbate. In particular, activated carbon adsorbants generally adsorb non-polar and chlorinated hydrocarbons in preference to unsaturated hydrocarbons such as ethylene or acetylene.
U.S. Pat. No. 2,255,752 (issued September 16, 1941 to G. Basel and E. Schaeffer) describes hydrogen chloride as an inert diluting gas suitable for use in admixture with acetylene (and chlorine) in the presence of porous charcoal at temperatures of 300.degree. to 400.degree. C.
U.S. Pat. No. 2,474,206 (issued June 28, 1949 to W. de Nie) describes the catalytic combination of hydrogen chloride and acetylene over an adsorptive substrate (such as activated carbon) impregnated with a mercury catalyst at temperatures above 100.degree. C.
Hydrochlorination catalysts require additional process steps to be fixed on suitable supports. In addition, mercuric chloride catalyst sublimes without decomposition at elevated temperatures and is capable of migrating off of a porous carbon substrate.
Hydrogen chloride has enhanced value if it is purified by removal of acetylene. It is desirable to develop a method of easily removing minor concentrations of acetylene from a hydrogen chloride gas stream.